Dedifferentiated liposarcoma with homologous lipoblastic differentiation

Abstract

Dedifferentiated liposarcoma is a distinct subtype of liposarcoma showing by transition from an atypical lipomatous tumor/well differentiated liposarcoma to non-lipogenic sarcoma of variable histologic grade. Recent studies have shown that the dedifferentiated component can show lipoblastic differentiation. We describe a case of dedifferentiated liposarcoma with homologous lipoblastic differentiation arising from the abdominal cavity. The patient was a 67-year-old woman who presented with the left lower quadrant abdominal mass for one month. Abdominal CT scan showed a well defined mass with heterogeneous signal intensity in the abdominal cavity. Excision of the mass was performed. Grossly, the mass measured 20 × 12 × 6cm. The cut surface was well circumscribed, yellow-brown, rubbery soft, with focal hemorrhage. Histologically, the tumor showed spindle and pleomorphic tumor cells in myxoid stroma with scattered lipoblasts. In addition, there were smaller foci of well differentiated liposarcoma showing atypical hyperchromatic stromal cells. The tumor cells in the dedifferentiated component were immunoreactive for MDM2 and CDK4. Fluorescence in situ hybridization showed high-level amplification of MDM2. Dedifferentiated liposarcomas with homologous lipoblastic differentiation should not be confused with pleomorphic liposarcomas and other types of pleomorphic sarcomas with fat component. We describe the histopathological features of liposarcomas.